A vinyl alcohol-based polymer (sometimes referred to as “PVA” below) is one of a few crystalline water-soluble polymers. Using the excellent water solubility and the film properties (strength, oil resistance, film formability, oxygen gas barrier property and the like), a PVA is widely used for emulsifiers, suspending agents, surfactants, fiber-processing agents, various binders, paper-processing agents, adhesives, films and the like. Regarding films of the uses, some applications for water-soluble films making use of the excellent water solubility are known.
In an example method, a unit amount of a chemical or the like such as an agricultural chemical and a detergent is sealed and packaged in a film (unit packaging), and when the content is used, the package is directly put into water and the content is dissolved or dispersed in water together with the packaging film. Advantages of the unit packaging are that hazardous chemicals can be used without directly touching the chemicals, that the measurement of the amount to be used is not necessary because a certain amount is packaged and that post-treatment of the packaging container, the bag or the like is not necessary or easy, for example.
In addition to the unit packaging, a method of using a liquid transfer printing film obtained by forming a print layer to be transferred on a surface of a water-soluble or water-expansive film such as a PVA film is known as means for forming a print layer on the surface of a molded item with an uneven three-dimensional surface or a curved surface to print a design or improve the surface properties. For example, PTL 1 describes a method for transferring a print layer to a surface of an object to be printed using liquid pressure by floating a liquid transfer printing film on the surface of a liquid, which is typically water, with the printed surface facing upwards and then pushing a molded item, which is the object to be printed, into the film from above.